The invention relates generally to a copier.
More particularly, the invention relates to a photographic copier, especially a so-called roll copier in which the originals to be copied and the copy paper are supplied from respective rolls.
A known photographic copier has a first support defining a first support plane in which the originals are disposed during copying. A second support defines a second support plane in which the copy paper is located for copying. The first and second supports are spaced from one another by a fixed distance, and an objective of variable focal length is situated between the supports. The objective is designed such that a sharp image of an original in the first plane may be formed in the second plane at a variety of magnifications.
Mounting of the original and copy paper supports at a fixed distance from one another has significant advantages for transport of the originals and the copy paper. This is especially true in roll copiers. However, it is frequently necessary for copiers to be capable of achieving a large number of magnifications in order to permit originals of different size to be reproduced on copy paper having a variety of sizes. In so-called universal printers, the number of magnifications required just to make borderless copies may be of the order of one hundred.
It is known to achieve a variety of magnifications using an adjustable objective. According to the teachings of the West German Offenlegungsschrift No. P 33 39 960, such an objective may include two lenses which, without affecting image sharpness, produce different magnifications depending upon their positions along the optical axis. However, adjustment of the magnification requires very precise positioning of the lenses. Moreover, positioning of the lenses is complicated by the fact that this must be accomplished differently for the two lenses due to tolerances in the lens-to-image distances of the individual lenses. The controls required for adjustment of the magnification are thus very expensive.